During pregnancy, maternal diet, drinking, and smoking may exert a powerful effect on fetal growth and development. The continued growth of the nursing infant makes investigation of these habits in lactation of paramount importance. This research is an interdisciplinary investigation of patterns of maternal diet, alcohol, and tobacco use during lactation, and the relationship of these patterns to infant growth and development. Women in the sixth month of pregnancy will be screened by mail alcohol and tobacco use and plans to lactate. First, a pilot study of 100 women will be conducted to test validity, reliability, and feasibility of methods and instruments. Then a sample of 200 currently lactating women and 200 women who have never lactated will be drawn. Maternal nutrient intake, food choices, cravings and aversions, and alcohol and tobacco use will be measured in a personal interview at 1 month post-partum. Data on these variables will also be gathered at 2 and 3 months post-partum. Differences in the variables between lactating and non-lactating women will be compared, and relationships among the variables explored. A follow-up at one year will obtain current estimates of both maternal and infant nutrient intake to determine how the two are related. Assessment of the relationship of alcohol and tobacco use during lactation to infant development will explored in a sample, stratified on frequency of use of these variables both during and after pregnancy, and on lactation status. Subjects will be contacted and interviewed as described above. Infants will be examined at one year to assess psychological and physical development. Infants of mothers who drank (or smoked) during lactation will be compared to infants whose mothers did not. If differences in growth and development exist, confounding variables will be examined to determine if they might account for the observed differences. Additional analyses will evalute the role of environmental factors, and the relative effects of prenatal and postnatal exposure.